Probiotics in Pregnancy Cut Allergies in Tots

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Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

This study suggests that intake of probiotic lactobacilli during pregnancy may modify atopic eczema and allergy development in early childhood.

SAN ANTONIO -- When mothers in Norway ate probiotic-enhanced dairy products while pregnant, their children were less prone to eczema and nasal allergies during infancy and toddlerhood, a researcher said here.

Results of the Norwegian Mother and Child Cohort Study indicated that, among mothers who consumed milk and yogurt fortified with probiotic bacteria, the risk of atopic dermatitis at 6 months was reduced 7% (adjusted relative risk 0.93, 95% CI 0.88 to 0.99) and the risk of rhinoconjunctivitis at ages 18-36 months was reduced by 12% (RR 0.88, 95% CI 0.78 to 0.98), reported Randi Bertelsen, PhD, of the Norwegian Institute of Public Health in Oslo.

Risk of atopic dermatitis at 18 months was the same in mothers who consumed these products during pregnancy and those who did not, she told attendees at the American Academy of Allergy, Asthma, and Immunology's annual meeting. But when the mothers used the products and also gave probiotic supplements to their children after 6 months of age, the risk was reduced significantly (RR 0.92, 95% CI 0.85 to 0.99).

The risks were adjusted to control for maternal factors including age, education, smoking status, body mass index at conception, dietary fiber intake, breastfeeding, parity and history of asthma and allergy, as well as infant gender and type of delivery.

Several previous studies had found that probiotics used by mothers and/or their offspring may reduce risk of childhood allergy and infections. But much of the evidence has been tenuous, Bertelsen said, with "consensus reports and a Cochrane review" indicating that more and better research is needed.

The Norwegian Mother and Child Cohort Study offered an ideal platform to test the connection, she suggested. It's a large, ongoing observational study that enrolled some 108,000 pregnant women and their children from 1999 to 2008.

Mothers participating in the study completed detailed food-frequency and lifestyle questionnaires, and their medical histories and those of their children could be obtained from Norway's comprehensive registry system. Just under 41,000 mother-child pairs were included in the current analysis.

Participants completed the food-frequency questionnaires at gestational week 22. Postnatal data were collected at months 6, 18, and 36, which included parental reports on the presence of eczema, "hay fever," asthma, and lower respiratory tract infections in their children. Mothers were also asked if they gave probiotic foods or supplements to the children.

Most of the mothers' probiotic consumption was in the form of yogurt and milk, Bertelsen said. About 37% of the women included in the study reported using these products regularly, whereas only 0.4% indicated that they took probiotic supplements in capsule form.

The dairy products were fortified with standard Lactobacillus acidophilus and L. rhamnosus and Bifidobacterium lactis strains.

Some 18% of mothers -- essentially all of whom took probiotics themselves -- said they also gave probiotic products to their children after age 6 months.

None of the analyses showed a relationship between probiotics and risk of asthma or lower respiratory infections, Bertelsen said.

Among the other factors examined in the analysis, one that stood out was the mode of delivery. Among children born vaginally to probiotic-consuming women, risks of eczema and rhinoconjunctivitis were reduced significantly (RR 0.94 and 0.87, respectively, both P<0.05). For children delivered by caesarean section, however, the risk reductions were nonsignificant.

But that may have been a statistical artifact, Bertelsen's data suggested. More than 35,000 of children in sample were born vaginally, compared with about 5,500 born by C-section. The point estimate for the relative risk of eczema in the C-section group, 0.92, was actually lower than the 0.94 seen in the vaginal-birth children, but the wider confidence interval rendered it nonsignificant. For rhinoconjunctivitis, the relative risk was only slightly larger with C-section compared with vaginal birth (0.92 versys 0.87).

Bertelsen said that a difference based on delivery mode was nevertheless plausible. Newborns receive an inoculation of bacteria at birth from the mother's vaginal flora during normal delivery, which does not occur with C-section.

Another route by which maternal intake of probiotics could affect infants is through breastfeeding. Bertelsen noted that previous studies have found that probiotic bacteria consumed by mothers can make their way into breast milk. Probiotics also have been found to increase interleukin-10 levels in breast milk, which in turn could serve to dampen allergic reactions in breastfed infants.

An important limitation of the study, she said, was that it did not have longer follow-up. She noted that colonization by exogenous probiotic bacteria is "not permanent."

Whether the apparent protective effect in children lasts beyond 18-36 months of age remains unclear, as does the question of whether it can be maintained by continued probiotic administration.

The analysis was funded by the Norwegian ministries of health and education and research and the National Institutes of Health.

Bertelsen declared she had no relevant financial interests.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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